FIELD OF THE INVENTION
The invention relates to a burner, particularly for a gas turbine, with a catalytic combustion chamber. The invention also relates to a gas turbine having the burner.
In such a device, a hydrocarbon and/or a hydrogen-containing energy medium is provided both in liquid and in gaseous form as a fuel. The fuel may be natural gas, petroleum or methane, for example. Such a burner can preferably be used in a gas turbine.
A gas turbine conventionally includes a compressor part, a burner part and a turbine part. The compressor part and the turbine part are usually disposed on a common shaft which at the same time drives a generator for generating electricity. Preheated fresh air is burnt in the compressor part together with a fuel of the above-mentioned type. The hot burner exhaust gas is fed to the turbine part and is expanded there.
Detailed information regarding the structure and use of a gas turbine is found in a company publication entitled "Gas turbines and Gas turbines Power Plants" of Siemens AG, May 1994, Order number A 96001-U 124-V 1-7600.
Nitrogen oxides NO.sub.x also occur as particularly undesirable combustion products in the combustion of a fuel of the type mentioned above. The nitrogen oxides, along with sulfur dioxide, are the main cause of the environmental problem of acid rain. Consequently, as well as in view of strict statutory norms on limit values for the emission of NO.sub.x, the aim is to keep the NO.sub.x emission of a gas turbine particularly low and, at the same time, to avoid appreciably influencing the power of the gas turbine.
Thus, for example, a lowering of the flame temperature in the burner has the effect of reducing nitrogen oxide levels. In this case, steam is added to the fuel or to the compressed and preheated fresh air, or water is injected into the combustion space. Such measures, which per se decrease the emission of nitrogen oxides, are referred to as primary measures for the abatement of nitrogen oxides.
Accordingly, the term "secondary measures" is used to describe all of those measures in which nitrogen oxide levels in the exhaust gas, for example of a gas turbine, or basically of a combustion process, are decreased through the use of subsequent measures.
In that respect, the method of selective catalytic reduction (SCR) has gained acceptance throughout the world. In that method, the nitrogen oxides are brought into contact with a reducing agent, usually ammonia, on a catalyst and form nitrogen and water. The use of that technology therefore necessarily entails the consumption of reducing agent. The nitrogen oxide abatement catalysts disposed in the exhaust-gas duct naturally cause a pressure drop which results in a power drop when the burner is used in a turbine. In the case of a gas turbine power of 150 MW, for example, and a retail electricity price of about $0.016/kWh (and about 0.15 DM/kWh in Germany, for example) for electrical energy, even a power drop amounting to a few parts per thousand has a serious effect on the result which can be achieved with such apparatus.
Published UK Patent Application GB 2 268 694 A provides a catalytic combustion chamber as a primary measure for the abatement of nitrogen oxides. The ignition temperature of fuel is lowered through the use of partial catalytic oxidation. The catalysts which are provided for this purpose are installed transversely to the direction of flow of the fuel and extend over the entire flow cross-section. This gives rise to high flow resistance.
Therefore, in the above-described burners, there is basically the problem of any nitrogen oxide abatement of a primary or a secondary nature which is provided there resulting in a power loss or a loss of overall efficiency in the gas turbine plant.